Information about Satellite Internet Access
Satellite Internet services are used in locations where terrestrial Internet access is not available and in locations which move frequently. Internet access via satellite is available worldwide, including vessels at sea and mobile land vehicles. There are three types of satellite Internet service:
Often, non-standard IP stacks are used to address the latency and asymmetry problems of the satellite connection. Data sent over the satellite link is generally also encrypted, as otherwise it would be accessible to anyone with a satellite receiver.
Many IP-over-satellite implementations use paired proxy servers at both endpoints so that clients and servers do not need to accept the latency inherent in a satellite connection. For similar reasons, there exist special Virtual private network (VPN) implementations designed for use over satellite links because standard VPN software cannot handle the long packet travel times.
Upload speeds are limited by the user's dial-up modem, and latency is high, as it is for any satellite based Internet. Download speeds can be very fast compared to dial-up:1 Mbits,4 Mbits,16 Mbits packages are generally offered.
Remote sites use the proxy server at the earth station (teleport), which is configured to route all outbound traffic to the QoS server, which makes sure no user exceeds their allotted bandwidth or monthly traffic limits. Traffic is then sent to the encapsulator, which puts the IP packets inside of DVB packets. The DVB packets are then sent to the DVB modem and then to the transmitter (BUC).
Each remote location is also equipped with a telephone modem; the connections for this are as with a conventional dial-up ISP. Two way satellite systems may sometimes use the modem channel in both directions for data where latency is more important than bandwidth, reserving the satellite channel for download data where bandwidth is more important than latency, such as for file transfers.
Uplink speeds rarely exceed one megabit per second and latency can be up to one second. Satellite phone services such as Iridium also provide data services at the comparatively slow speed of 2400 bit/s.
International Mobile Satellite Organization (INMARSAT) offers three bidirectional satellite internet services called Broadband Global Area Network (BGAN), Regional BGAN and MPDS, neither of which have to be precisely aligned but the speeds are lower than the dish-based systems and bandwidth costs are much higher. BGAN has the highest data rate. Thuraya offers a similar service but this is not as fast as BGAN.
In 2006 the European Commission sponsored the UNIC project which aims at developing an end-to-end scientific test bed for the distribution of new broadband interactive TV-centric services delivered over low-cost two-way satellite to actual end-users in the home. The UNIC architecture employs DVB-S2 standard for downlink and DVB-RCS standard for uplink.
A theoretical alternative to satellites that is being explored is the use of ultra-light solar powered airplane (see the NASA Pathfinder) that could fly in a continuous, circling path perhaps 70,000 feet (20 km) high or an airship (see Stratellite). These would act as flying satellites, providing high-speed service to customers below the aircraft. Since the roundtrip signal distance would only be 30 miles (0 km), the latency caused by the speed of light is an almost insignificant 0.1 ms under the craft, and 2 ms at the edge of the covered area, at a 300 km (200 miles) distance. Such service via aircraft is still in the experimental stages as of 2006.
Another practical method which can lower latency is to configure the satellite with a robust computer and cache. Much of the slowdown associated with satellite Internet is that for each request, many roundtrips must be completed before any useful data can be received by the requester.[1] A well-maintained cache located in space would alleviate many of the full round-trips. Caching would assist in speeds as well; When cached data is requested, it takes less than half of the normal time to receive the response, speeding up the time normally wasted on mere latency. Of course, this method requires some forethought by the people who design the satellite - it is impractical to retrofit older satellites with new equipment such as this.
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- one-way multicast,
- one-way with terrestrial return, and
- very small aperture terminal (VSAT) (two-way) satellite access.
One-way multicast
One-way multicast satellite Internet systems are used for Internet Protocol (IP) multicast-based data, audio and video distribution. In the U.S., a Federal Communications Commission (FCC) license is required only for the uplink station and no license is required for users. Note that most Internet protocols will not work correctly over one-way access, since they require a return channel. However, Internet content such as web pages can still be distributed over a one-way system by "pushing" them out to local storage at end user sites, though full interactivity is not possible. This is much like TV or radio content which offers little user interface.System hardware components
Similar to one-way terrestrial return, satellite Internet access may include interfaces to the public switched telephone network for squawk box applications. An Internet connection is not required, but many applications include an File Transfer Protocol (FTP) server to queue data for broadcast.System software components
Most one-way multicast applications require custom programming at the remote sites. The software at the remote site must filter, store, present a selection interface to and display the data. The software at the transmitting station must provide access control, priority queueing, sending, and encapsulating of the data.One-way with terrestrial return
One-way terrestrial return satellite Internet systems are used with traditional dial-up access to the Internet, with outbound data traveling through a telephone modem, but downloads sent via satellite at a speed near that of broadband Internet access. In the U.S., an FCC license is required for the uplink station only; no license is required for the users.System hardware components
The transmitting station (also called "teleport", "head end", "uplink facility", or "hub") has two components:- Internet connection: The ISP's routers connect to proxy servers which can enforce quality of service (QoS) bandwidth limits and guarantees for user traffic. These are then connected to a DVB encapsulator which is then connected to a DVB-S modem. The radio frequency (RF) signal from the DVB-S modem is connected to an up converter which is connected via feed line to the outdoor unit.
- Satellite uplink: The block upconverter (BUC) and optional low-noise block converter (LNB), which may use a waveguide to connect to the optional orthomode transducer (OMT) which is bolted to the feed horn which is connected by metal supports to the satellite dish and mount.
- Outdoor unit
- Satellite dish with mount
- Feedhorn
- Universal LNB, for Ku band.
- Feed line
- Indoor unit
- DVB-S Peripheral Component Interconnect (PCI) card internal to a computer
- or, DVB external modem where an 8P8C (RJ-45) Ethernet port or a Universal Serial Bus (USB) port connects the modem to the computer
System software components
Remote sites require a minimum of programming to provide authentication and set proxy server settings. Filtering is usually provided by the DVB card driver.Often, non-standard IP stacks are used to address the latency and asymmetry problems of the satellite connection. Data sent over the satellite link is generally also encrypted, as otherwise it would be accessible to anyone with a satellite receiver.
Many IP-over-satellite implementations use paired proxy servers at both endpoints so that clients and servers do not need to accept the latency inherent in a satellite connection. For similar reasons, there exist special Virtual private network (VPN) implementations designed for use over satellite links because standard VPN software cannot handle the long packet travel times.
Upload speeds are limited by the user's dial-up modem, and latency is high, as it is for any satellite based Internet. Download speeds can be very fast compared to dial-up:1 Mbits,4 Mbits,16 Mbits packages are generally offered.
Theory of operation
)
The back panel of a satellite modem, with coaxial connections for both incoming and outgoing signals, and an Ethernet port for connection to the internal network.
Two-way
Two-way satellite Internet service sends data from remote sites via satellite to a hub, which then sends the data to the Internet. The satellite dish at each location must be precisely positioned to avoid interference with other satellites. The oscillators in some radar detectors can cause interference with these systems. Also, each location must use power management to adjust the amount of transmit power to compensate for things like rain fade. There are several types of two way satellite Internet services, such as time division multiple access (TDMA) or single channel per carrier (SCPC).Each remote location is also equipped with a telephone modem; the connections for this are as with a conventional dial-up ISP. Two way satellite systems may sometimes use the modem channel in both directions for data where latency is more important than bandwidth, reserving the satellite channel for download data where bandwidth is more important than latency, such as for file transfers.
Uplink speeds rarely exceed one megabit per second and latency can be up to one second. Satellite phone services such as Iridium also provide data services at the comparatively slow speed of 2400 bit/s.
International Mobile Satellite Organization (INMARSAT) offers three bidirectional satellite internet services called Broadband Global Area Network (BGAN), Regional BGAN and MPDS, neither of which have to be precisely aligned but the speeds are lower than the dish-based systems and bandwidth costs are much higher. BGAN has the highest data rate. Thuraya offers a similar service but this is not as fast as BGAN.
In 2006 the European Commission sponsored the UNIC project which aims at developing an end-to-end scientific test bed for the distribution of new broadband interactive TV-centric services delivered over low-cost two-way satellite to actual end-users in the home. The UNIC architecture employs DVB-S2 standard for downlink and DVB-RCS standard for uplink.
Reducing satellite latency
One solution is to use satellites in much lower orbit very close to the Earth, to shorten the travel distance. Such orbital paths are no longer geostationary, and so would require a large number of satellites in orbit so that at least one is visible in the sky at all times. Communication dishes could no longer be fixed, and would either need some way to track the satellites as they move across the sky, or to work in an omnidirectional manner without causing interference for anything else.A theoretical alternative to satellites that is being explored is the use of ultra-light solar powered airplane (see the NASA Pathfinder) that could fly in a continuous, circling path perhaps 70,000 feet (20 km) high or an airship (see Stratellite). These would act as flying satellites, providing high-speed service to customers below the aircraft. Since the roundtrip signal distance would only be 30 miles (0 km), the latency caused by the speed of light is an almost insignificant 0.1 ms under the craft, and 2 ms at the edge of the covered area, at a 300 km (200 miles) distance. Such service via aircraft is still in the experimental stages as of 2006.
Another practical method which can lower latency is to configure the satellite with a robust computer and cache. Much of the slowdown associated with satellite Internet is that for each request, many roundtrips must be completed before any useful data can be received by the requester.[1] A well-maintained cache located in space would alleviate many of the full round-trips. Caching would assist in speeds as well; When cached data is requested, it takes less than half of the normal time to receive the response, speeding up the time normally wasted on mere latency. Of course, this method requires some forethought by the people who design the satellite - it is impractical to retrofit older satellites with new equipment such as this.
References
See also
- Back-channel and return channel
- HughesNet (formerly DIRECWAY)
- Ts_2
- IP over DVB
- Satellite dish
- StarBand
- Very small aperture terminal
- WildBlue
- Voice over IP
- Virtual private network
- List of device bandwidths
- UNIC - UNIversal satellite home Connection
Internet access methods | |
|---|---|
| Wired: | Dial-up, ISDN, DSL, Cable, Fiber optic, Power-line internet |
| Wireless: | Wi-Fi, WiBro, WiMAX, UMTS-TDD, HSPA, EV-DO, Satellite |
Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government
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satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon.
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Oceania
Africa
Asia
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Simplex communication is a name for a type of communication circuit. There are two (contradictory) definitions that have been used for the term. In both cases, the other definition is referred to as half duplex.
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Multicast is the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the destinations split.
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Very Small Aperture Terminal (VSAT), is a two-way satellite ground station with a dish antenna that is smaller than 3 meters (most VSAT antennas range from 75 cm to 1.2 m). VSAT data rates typically range from narrowband up to 4 Mbit/s.
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Internet protocol may refer to:
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- The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork
- The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs
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Multicast is the delivery of information to a group of destinations simultaneously using the most efficient strategy to deliver the messages over each link of the network only once, creating copies only when the links to the destinations split.
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Motto
"In God We Trust" (since 1956)
"E Pluribus Unum" ("From Many, One"; Latin, traditional)
Anthem
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"In God We Trust" (since 1956)
"E Pluribus Unum" ("From Many, One"; Latin, traditional)
Anthem
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Federal Communications Commission
Logo
The FCC's official seal
Agency overview
Formed June 19, 1934
Preceding Agencies Federal Radio Commission
Annual Budget
Agency Executive
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Logo
The FCC's official seal
Agency overview
Formed June 19, 1934
Preceding Agencies Federal Radio Commission
Annual Budget
Agency Executive
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A Web page or webpage is a resource of information that is suitable for the World Wide Web and can be accessed through a web browser. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext links.
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The public switched telephone network (PSTN) is the network of the world's public circuit-switched telephone networks, in much the same way that the Internet is the network of the world's public IP-based packet-switched networks.
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Squawk Box, which debuted on CNBC in 1995, can refer to a number of television programmes broadcast by the CNBC group of television channels which air at breakfast time on their station of origin.
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FTP or File Transfer Protocol is used to transfer data from one computer to another over the Internet, or through a network.
Specifically, FTP is a commonly used protocol for exchanging files over any network that supports the TCP/IP protocol (such as the Internet or
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Specifically, FTP is a commonly used protocol for exchanging files over any network that supports the TCP/IP protocol (such as the Internet or
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hot Dial-up access is a form of Internet access via telephone line. The client uses a modem connected to a computer and a telephone line to dial into an Internet service provider's (ISP) node to establish a modem-to-modem link, which is then routed to the Internet.
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Modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information.
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high-speed Internet, because it usually has a high rate of data transmission. In general, any connection to the customer of 256 kbit/s (0.256 Mbit/s) or more is considered broadband Internet. The International Telecommunication Union Standardization Sector (ITU-T) recommendation I.
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In computer networks, a proxy server is a server (a computer system or an application program) which services the requests of its clients by forwarding requests to other servers.
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Quality of Service, abbreviated QoS, refers to resource reservation control mechanisms. Quality of Service can provide different priority to different users or data flows, or guarantee a certain level of performance to a data flow in accordance with requests from the
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DVB, short for Digital Video Broadcasting, is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the DVB Project, an industry consortium with more than 270 members, and they are published by a
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Radio frequency, or RF, is a frequency or rate of oscillation within the range of about 3 Hz and 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves.
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The Feed line in a radio transmission, reception or transceiver system is the physical cabling that carries the RF signal to and/or from the antenna. It is also called a transmission line.
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block up-converter (BUC) is used in the transmission (uplink) of satellite signals. It converts a band (or "block") of frequencies from a lower frequency to a higher frequency. Modern BUCs convert from the L band to Ku band, C band and Ka band.
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A low-noise block converter (LNB, for low-noise block, or sometimes LNC, for low-noise converter) is used in communications satellite (usually broadcast satellite) reception (downlink).
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A waveguide is a structure which guides waves, such as electromagnetic waves, light, or sound waves. There are different types of waveguide for each type of wave.
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Electromagnetic waveguides
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Andrew, Swedish Microwave units.
The following images show a Portenseigne & Hirschmann Ku band configuration, that highlights the horizontal the vertical, and circular polarised wave-guide ports that join to the Feed-horn, the LNB or BUC elements of an outdoor unit.
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The following images show a Portenseigne & Hirschmann Ku band configuration, that highlights the horizontal the vertical, and circular polarised wave-guide ports that join to the Feed-horn, the LNB or BUC elements of an outdoor unit.
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In satellite dish and antenna design parlance, a feedhorn (or feed horn) is a horn antenna used to convey radio waves between the transceiver (transmitter and/or receiver) and the reflector.
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satellite dish is a type of parabolic antenna designed with the specific purpose of transmitting signals to and/or receiving from satellites. A satellite dish is a particular type of microwave antenna.
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:
The Ku band (pronounced "kay-yoo"; Kurtz-under band) is a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 12 to 18 GHz..... Click the link for more information.
PCI
Peripheral Component Interconnect
five 32-bit PCI expansion slots on a motherboard
Year created: Mid-1993
Created by: Intel
Superseded by: PCI Express (2004)
Width:
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Peripheral Component Interconnect
five 32-bit PCI expansion slots on a motherboard
Year created: Mid-1993
Created by: Intel
Superseded by: PCI Express (2004)
Width:
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